In recent years, a so-called chemical mechanical polishing (CMP) technique for physically polishing and flattening a semiconductor substrate in producing a device is used in accordance with multilayer wiring on a surface of a semiconductor substrate. CMP is a method for flattening the surface of a polishing object (object to be polished) like a semiconductor substrate by using a polishing composition (slurry) containing abrasive grains such as silica, alumina, or ceria, an anti-corrosion agent, a surfactant, or the like. The polishing object (object to be polished) is silicon, polysilicon, silicon oxide film, silicon nitride, a wiring or a plug which consists of metal, or the like.
On the surface of a semiconductor substrate after CMP processing, residual impurities (defects) are present in a large amount. As for the impurities, there are abrasive grains, metals, an anti-corrosion agent and an organic material such as a surfactant that are derived from a polishing composition used for CMP, a silicon-containing material or a metal which is generated according to polishing of a silicon-containing material, metal wirings or plug as a polishing object, and also an organic material such as pad debris which is generated from various pads.
Once the surface of a semiconductor substrate is contaminated with those impurities, an adverse effect may be exhibited on electrical properties of a semiconductor, and thus there is a possibility of having lower device reliability. In addition, if contamination by organic materials is significant, breakage of a device may be caused. Thus, it is necessary to remove those impurities from the surface of a semiconductor substrate by introducing a cleaning step after CMP step.
For a cleaning step, a cleaning agent is used to remove those impurities from the surface of a semiconductor substrate, and various kinds of cleaning agent have been developed so far (see, Patent Literature 1)